| Electromagnetic radiation rock failure process started around the 1970 s,mainly in earthquake prediction,coal mine safety monitoring and other fields.However,the mechanism of this process is very complex,and the current results of earthquake monitoring and rock tests are not clear on electromagnetic effect mechanism.Especially,the charactersitics of electromagnetic signals from different types of rock is still lack comparative research.Thus,to investigate the influence of rock property on the electromagnetic radiation mechanism of rock fracture is one of the important research fields of solid mechanics.It is significant also for academic study.The main contents are as follows:(1)Theoretical explantions and experimental results of electromagnetic radiation from rock fracture are summarized,respectively from seismic observations and laboratory tests.Several characteristics of the signals are concerned,including the frequency distribution,the appearance and duration,the directional difference,and distinctions between different types of rocks.A set of experimental system for observation of electromagnetic signals fromprocess of rock fracturing was independtly developed.The test system includes electromagnetic shielding,signal sensing and transmission,signal collecting and loading system.Lithology of granite,basalt,sandstone and marble was analyzed.The mechanical parameters of elastic modulus,compressive strength,Poisson's ratio,fracture toughness and tensile strength of the four types rocks were tested.(2)Self-expanding destructive experiments of different rocks were conducted.The crack morphology of different lithological rocks was analyzed.The influence of rock property to the characteristics of self-expanding fracturing was summarized.Charactersitcs of electromagnetic radiation of rock fracturing was summed up.Electromagnetic waveform,radiation intensity and frequency radiation were statistical analyzed.The influence of different rock properties to the electromagnetic radiation mechanism of rock fracturing was revealed.(3)Based on the rock stress concentration polarization,introducing the crack tip stress and displacement field,combing the Hertz electromagnetic oscillator,the formula of rock cracking electromagnetic waveform was generated.Therelationship between the electromagnetic signal strength and rock mechanics parameters,the radiation intensity in different directions,the relationship between signal strength and frequency wereanalyzed.The theoretical results arepreferably agreement with the experimental results. |
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